Concrete reinforcing rods are usually bound together with wire prior to pouring cement. Currently, the wire is often cut and installed on the bars by hand. The automatic tools that are available either produce a loose tie or are unreliable in construction environments because of the complex mechanisms required to twist and tie wire.
U.S. Pat. No. 3,323,558 to Collins for example discloses a wire tying apparatus that uses a twist pin to twist the wire. The Collins tool does not have any mechanism for holding the ends of the wires when they are being twisted. The ends of the wire are free in the cross opening of the twist pin.
U.S. Pat. No. 4,117,872 to Gott et al for example discloses a wire twisting device that uses a variable position jaw mechanism and a rotatable twisting head. Both mechanisms involve precise mechanical movements and parts.